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81.
Bajaj VS Farrar CT Hornstein MK Mastovsky I Vieregg J Bryant J Eléna B Kreischer KE Temkin RJ Griffin RG 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,160(2):85-90
In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g=2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170+/-50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of approximately 17 have been obtained in two-dimensional 13C-13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. 相似文献
82.
Indira Chatterji 《Geometriae Dedicata》2003,96(1):161-177
We apply V. Lafforgues techniques to establish property (RD) for cocompact lattices in a finite product of rank one Lie groups with Lie groups whose restricted root system is of type A
2. 相似文献
83.
Relationship between topochemical indices and inhibition of CDK2/cyclin A by 3-aminopyrazoles was investigated using a data set comprising of 42 3-aminopyrazoles. Three topochemical indices--the Wiener's topochemical index--a distance based topochemical index, atomic molecular connectivity index--an adjacency based topochemical index and superadjacency topochemical index--an adjacency-cum-distance based topochemical index were used for the present investigations. The values of Wiener's topochemical index, atomic molecular connectivity index and superadjacency topochemical index for each of the 42 compounds comprising the data set were computed using an in-house computer program. Resultant data was subsequently analyzed and suitable models were developed after identification of the active ranges. Subsequently, a biological activity was assigned to each of the compounds using these models, which was then compared with the reported CDK2/cyclin A inhibitory activity. High accuracy of prediction ranging from 86 to 89% was observed using these models. 相似文献
84.
Summary The present results confirm conclusively the inference drawn earlier [2] regarding the role of adsorption of zinc ions on the basis of galvanostatic studies on solid substrates which is also the conclusion drawn by Yurev and Volkov [3] by their recent work on solid substrates.
Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday. 相似文献
Zusammenfassung Bei galvanostatischen Untersuchungen an festen Medien über die Bedeutung der Adsorption von Zinkionen konnten die Ergebnisse einer früheren eigenen Arbeit [2] sowie der Arbeit von Yurev u. Volkov [3] bestätigt werden. Aufgrund potentiodynamischer und potentiostatischer Versuche mit der Quecksilber-Tropfelektrode konnte festgestellt werden, daß die Abscheidungsgeschwindigkeit von Nickel aus Nickelbädern durch Zusatz von Zinkionen herabgesetzt wird. Die Vorteile einer Quecksilber-Tropfelektrode für solche Untersuchungen werden aufgezeigt und interessante Besonderheiten im Verhalten der Strom-Zeit-Kurve während des Wachstums des Tropfens diskutiert.
Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday. 相似文献
85.
Summary Synthesis of MHNAMT [3-methyl-4-(2-hydroxy-1 naphthalideneamino)-5-mercapto-1,2,4-triazole] and its IR and NMR spectral data are reported. The high stability of the characteristically coloured chelates with Cu(II), Co(II), Ni(II), Pd(II), Pt(IV) and Rh(III) has been made the basis for their efficient ascending TLC separations on silica gel G layers, when present together. Results of three different solvent systems are included to assess efficient resolution of the chelates. 相似文献
86.
We present measurements of the Nusselt number N as a function of the Rayleigh number R in cylindrical cells with aspect ratios 0. 5=gamma identical withD/d=12.8 ( D is the diameter and d is the height). We used acetone with a Prandtl number sigma = 4.0 for 10(5) less, similarR less, similar4x10(10). A fit of a power law N = N(0)R(gamma(eff)) over limited ranges of R yielded values of gamma(eff) from 0.275 near R = 10(7) to 0.300 near R = 10(10). The data are inconsistent with a single power law for N(R). For R>10(7) they are consistent with N = asigma-1/12R1/4+bsigma-1/7R3/7 as proposed by Grossmann and Lohse for sigma greater, similar2. 相似文献
87.
88.
D.C. Reynolds D.W. Langer C.W. Litton G.L. McCoy K.K. Bajaj 《Solid State Communications》1983,46(6):473-476
A self-reversal model is presented to explain the luminescence dependence of the donor bound exciton intensity. The line broadening mechanism is attributed to rotational interaction with non-rigid rotator states. Line reversal results from absorption by non-broadened states near the crystal surface. The absence of a similar excitation intensity dependence for acceptor bound excitons is explained. 相似文献
89.
D.C. Reynolds C.W. Litton E.B. Smith P.W. Yu K.K. Bajaj 《Solid State Communications》1982,42(11):827-830
Recombination radiation due to an exciton bound to neutral donors and neutral acceptors in high purity vapor phase epitaxial GaAs is investigated using high resolution photoluminescence spectroscopy at liquid helium temperatures. It is found that those samples which show the presence of germanium acceptors also exhibit a strong residual donor referred to in the literature as X3. Samples containing carbon acceptors however, do not show the presence of X3. In the past X3 has been identified by some groups as due to carbon on the gallium site. The work presented here sugests that the X3 donor is associated with germanium. This identification of the X3 donor is in agreement with a recent assignment based on the far infrared study of neutron transmuted GaAs. 相似文献
90.
The Raman and infrared spectra of N, N-dimethylthioformamide and N, N-dimethylthioacetamide were recorded and the vibrational frequencies are assigned. The normal co-ordinate treatment of these molecules has been carried out and the potential energy distributions calculated in order to clarify the nature of normal vibrations and investigate the magnitude of mixing up of various skeletal frequencies. The results in regard to the nature of the C-N and C=S stretching frequencies in these thioamides are compared with those of primary and secondary thioamides on the one hand and those of the corresponding ordinary tertiary amides on the other. It has been shown that the force constants of the general quadratic force field type are transferable in the series of molecules of tertiary amides and tertiary thioamides. The lowest frequency in the region of 150 cm.?1 to 160 cm.?1 has been recorded by the authors in the Raman spectra of the two tertiary thioamides under consideration. In the normal vibrational analysis of related molecules, the earlier workers only calculated this frequency, but did not record it. 相似文献